Traffic delays at Seaway Drive and the railroad tracks in Fort Pierce — for motorists headed east to the barrier island — would nearly triple if All Aboard Florida begins running passenger trains through the Treasure Coast, according to traffic experts and the Federal Railroad Administration.

Peak-hour traffic, which now grinds to a standstill 4 minutes of every hour, would hit gridlock for 11½ minutes if All Aboard Florida begins cutting through Fort Pierce, according to the federal Environmental Impact Statement for All Aboard Florida, which was issued Sept. 19.

Traffic coming westbound to the mainland, which now is delayed 2½ minutes each peak hour by freight trains, would see 7½ minutes of delays if All Aboard Florida begins as planned in 2017

Freight trains — run by All Aboard Florida sister company Florida East Coast Railway — already can tie up northbound U.S. 1 traffic at least a city block back from Seaway Drive, leaving drivers sitting several minutes in the right lane, waiting for the train to pass.

Traffic delays on Seaway Drive would be the worst among 15 rail crossings studied, according to the report, which called the added traffic congestion “unavoidable.”

The report details the effect 32 trains a day would have on the Treasure Coast. No stops are planned for Indian River, Martin and St. Lucie counties along the 235-mile route from Orlando to Miami.

Local governments in St. Lucie, Indian River and Martin counties have passed resolutions opposing the trains.

The trains would create “some degradation” in the level of service at grade crossings, the report concedes. With more than three trains per hour at some locations, “greater percentages of those hours would operate under unacceptable levels of service.”

The worst stretches of delays would grow from 2½ minutes to 7½ minutes each peak hour at Oslo Road in Indian River County; from 2 to 6½ minutes at the eastbound and westbound State Road 60 crossings in Vero Beach; and from 2 to 5½ minutes at the Indian Street/Dixie Highway crossing in Stuart.

Most of the other crossings studied also showed anticipated increases in wait times.

All Aboard Florida has 78 grade crossings on the Treasure Coast.

The passenger trains would create “minor degradation of local road traffic conditions at certain at-grade crossings and nearby intersections,” the report said.

Traffic delays would be expected even without the addition of All Aboard Florida, the report said. Freight traffic is expected to grow from 14 trains a day to 20 trains by 2016, according to the report.

“The projected annual increase in freight would result in minor increases in local roadway crossing closures, but total impacts relative to existing conditions would be minimal,” the report states.

Freight-train closures — now averaging 1.2 minutes per hour — would grow to 2½ to 2.8 minutes per hour, the report said.